KR101792824B1 - Bidirectional converter - Google Patents

Bidirectional converter Download PDF

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Publication number
KR101792824B1
KR101792824B1 KR1020150151312A KR20150151312A KR101792824B1 KR 101792824 B1 KR101792824 B1 KR 101792824B1 KR 1020150151312 A KR1020150151312 A KR 1020150151312A KR 20150151312 A KR20150151312 A KR 20150151312A KR 101792824 B1 KR101792824 B1 KR 101792824B1
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KR
South Korea
Prior art keywords
link
voltage
unit
stage
switch
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KR1020150151312A
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Korean (ko)
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KR20170050151A (en
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안희원
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삼성중공업 주식회사
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters

Abstract

The present invention relates to a bidirectional power conversion apparatus capable of solving a voltage unbalance phenomenon occurring in a multi-level type converter. The bidirectional power conversion apparatus includes a transformer connected to the transformer for receiving a voltage from a high-voltage power source and a transformer connected to the transformer for rectifying the alternating current into direct current or converting the direct current to alternating current, And a second DC link stage connected in series with the first DC link stage to form a neutral point and a second DC link stage connected in parallel to the DC link section to control a voltage level of the DC link section And an inverter unit connected in parallel to the control unit and the DC link unit to convert the DC output from the DC link unit into AC and supply the DC output to the lower stage or rectify the back electromotive force received from the lower stage to DC and supply the DC to the DC link unit.

Figure R1020150151312

Description

[0001] Bidirectional converter [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional power conversion apparatus, and more particularly, to a bidirectional power conversion apparatus capable of solving a voltage unbalance phenomenon occurring in a multilevel type converter.

The main power supply for stable operation of the load is a multi-level converter such as a two-level converter and a three-level converter.

Among them, a three-level converter of a NPC (Neutral Point Clamped) structure is the most commonly used structure of a power conversion device. The 3-level converter is composed of a rectifying section composed of a plurality of diodes, a dc link section composed of a plurality of capacitors, and an inverter section constituted by a plurality of power semiconductor elements and diodes. This three-level converter has a merit that the magnitude of the instantaneous voltage fluctuation (dv / dt) can be reduced by connecting a diode to the neutral point formed in the dc link portion to limit the voltage applied to the power semiconductor.

However, when the rectifying part of the 3-level converter is formed and operated with the same power semiconductor element as the inverter part, not the diode, the voltage between the capacitors constituting the dc link part becomes unbalanced, have.

Therefore, in order to solve this problem, various researches and developments are currently under way in order to balance the voltage of the dc link part. For example, a technique has been developed to adjust the voltage balance of the dc link portion through a control method of a controller that controls a power semiconductor, that is, a control algorithm. However, since the developed control method has a limit value of the voltage that can be synthesized in the power semiconductor of the inverter by using the voltage value of the dc link part, there is a limit to make the voltage of the capacitor of the dc link part to be in a perfectly balanced state.

Korean Patent Publication No. 10-2010-7023012 (January 18, 2010)

SUMMARY OF THE INVENTION The present invention is directed to a bidirectional power conversion apparatus capable of solving the voltage unbalance phenomenon of a plurality of DC link stages included in a three-level converter.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a bidirectional power conversion apparatus comprising: a transformer receiving a voltage from a high voltage source and transforming the transformed voltage; a converter connected to the transformer for rectifying AC into direct current or converting direct current into AC; And a second DC link stage connected in parallel with the first DC link stage to store rectified electrical energy and a second DC link stage connected in series with the first DC link stage to form a neutral point, And a voltage control unit connected in parallel to the second DC link stage and controlling the voltage magnitude of the DC link unit, a DC link unit connected in parallel to the DC link unit to convert the DC output from the DC link unit into AC, Or an inverter unit for rectifying the counter electromotive force introduced from the negative terminal to a direct current and supplying the rectified direct current to the direct current link unit .

The voltage control unit may further include a semiconductor switch and a charge storage unit connected in parallel to the semiconductor switch to store electrical energy.

Wherein the charge storage section includes a first charge storage section connected to the anode of the first DC link stage and the neutral point and a second charge storage section connected to the neutral point and the cathode of the second DC link stage, The storage unit and the second charge storage unit may be devices having the same electrical characteristics as the DC link unit.

The converter unit and the inverter unit include a plurality of legs connected in series to a plurality of semiconductor switches in a diode-connected fashion, and the legs may be connected in parallel with each other.

Wherein the leg portion is connected in series with a first switch, a second switch, a third switch and a fourth switch, the first diode is connected in anti-parallel to the connection point of the first switch and the second switch and the neutral point, And a second diode connected in series with the first diode, the second diode being connected in parallel to the connection point of the third switch and the fourth switch and the neutral point.

The bidirectional power conversion apparatus according to the present invention adjusts the voltages of the DC link ends of the upper and lower ends to be balanced so that the inverter section interlocked with the DC link stage can be smoothly operated.

1 is a circuit diagram of a bidirectional power conversion apparatus according to an embodiment of the present invention.
2 is a diagram showing a voltage unbalance state in which the first DC link end of FIG. 1 is overcharged than the second DC link end.
FIG. 3 is a graph showing voltage magnitudes charged in the first DC link stage and the second DC link stage of FIG. 2. FIG.
4 is a diagram showing a voltage unbalance state in which the second DC link end of FIG. 1 is overcharged than the first DC link end.
FIG. 5 is a diagram showing the magnitude of the voltage charged in the first DC link end and the second DC link end in FIG.
FIG. 6 is a diagram illustrating voltage balance states of the first DC link stage and the second DC link stage by operating the first voltage control stage and the second voltage control stage of FIG. 1;
FIG. 7 is a diagram illustrating voltage magnitudes output from the first DC link stage and the second DC link stage of FIG. 6. FIG.

Brief Description of the Drawings The advantages and features of the present invention and methods of achieving them can be made clear with reference to the embodiments described below in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. To fully disclose the scope of invention to a person skilled in the art, and the invention is only defined by the claims. Like reference numerals refer to like elements throughout the specification.

Hereinafter, a bidirectional power conversion apparatus according to an embodiment of the present invention will be described in detail with reference to FIG.

1 is a circuit diagram of a bidirectional power conversion apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a bidirectional power conversion apparatus 1 according to an embodiment of the present invention includes a voltage control unit 40 connected to a DC link unit 30 to control a neutral voltage formed in a DC link unit 30 Thus, it is possible to solve the voltage unbalance shape generated in the multi-level type power converter. Therefore, the bidirectional power conversion apparatus 1 enables the inverter unit 50, which uses the voltage of the DC link unit 30 and synthesizes by AC, to operate smoothly.

This bidirectional power conversion apparatus 1 includes a transformer 11 and a converter 22 connected to the transformer 11 for converting a voltage from the high voltage source 10 to a voltage, And includes an LC filter portion 21 capable of passing a signal component in a low-frequency region. The bidirectional power conversion apparatus 1 further includes a DC link unit 30 including a first DC link stage 31 and a second DC link stage 32 connected in parallel to the respective converter units 22, A first voltage control stage 41 and a second voltage control stage 42 connected in parallel to the DC link stage 31 and the second DC link stage 32 and an inverter section 40 connected in parallel to the DC link section 30, (50), and the like.

Here, the converter section 22 and the inverter section 50 may all be semiconductor switches having the same electrical characteristics. For example, the semiconductor switch may be any one of IGBT, IEGT, MOSFET, ICGT, GCT, SGCT, and GTO. In this specification, an IGBT which is easy to drive and has high efficiency at high voltage and large current is used as an example of a semiconductor switch. The IGBT has a gate, an emitter and a collector terminal, and a controller is installed at the gate terminal to convert the voltage while the IGBT is switched on or off.

The high-voltage voltage source 10 is formed by a wire connection, and can be a power source capable of outputting a high voltage such as 3.3 kV. The high voltage source 10 is connected to a transformer 11 that changes the magnitude of the voltage and can apply a voltage to the transformer 11.

The transformer 11 is formed in a wire-wired manner so that the phase voltage is 1/3 times the line-to-line voltage and the high voltage can be easily applied to the converter unit 22. The transformer (11) is not limited to the wye-wire type, and the transformer (11) is changed to the delta wiring method in the case of a wiring system capable of transmitting a large current whose secondary phase current is 1 / .

The LC filter unit 21 may include a plurality of capacitors connected in parallel with the transformer 11 and an inductor connected in series to the capacitors. The LC filter unit 21 removes components within a specific range of the power source applied from the transformer 11 and applies the removed components to the converter unit 22. [

The converter section 22 serves to convert the AC power applied through the LC filter section 21 to DC power. The converter section 22 is formed in a structure in which a plurality of semiconductor leg portions 22a to 22c connected in parallel with the diodes D C1 to D C12 are connected in parallel to a plurality of semiconductor switches T C1 to T C12 . The converter section 22 is connected to the transformer 11 to convert the alternating current applied from the transformer 11 into a DC signal through the operation of the plurality of semiconductor switches T C1 to T C12 and the diodes D C1 to D C12 And can be rectified and transmitted to the DC link unit 30.

The DC link unit 30 is formed in a structure in which the first DC link stage 31 and the second DC link stage 32 are connected in series and the charge corresponding to the full- . Furthermore, the DC link unit 30 can suppress the voltage fluctuation due to the ripple current supplied from the converter unit 22, and supply the DC voltage of a predetermined magnitude to the inverter unit 50. [ At this time, the first direct current link end 31 and the second direct current link end 32 are charged with the electric energy which is moved according to the switch operation of the converter part 22.

Here, the first DC link stage 31 and the second DC link stage 32 are polarized and not only capable of charging the same amount of charge per hour, but also capable of emitting the same amount of charge per hour It can be an electrolyte capacitor. The first DC link stage 31 and the second DC link stage 32 are provided with a voltage control unit 40 in parallel so that the first DC link stage 31 and the second DC link stage 31, The voltage state of the DC link stage 31 can be in an equilibrium state.

The voltage control unit 40 includes the semiconductor switches 41T and 42T, the diodes 41D and 42D connected in anti-parallel to the semiconductor switches 41T and 42T, and the charge storage units 41C and 41C connected in parallel to the semiconductor switches 41T and 42T. A first voltage control stage 41 connected in parallel with the first DC link stage 31 and a second voltage control stage 42 connected in parallel with the second DC link stage 32, . At this time, the first voltage control stage 41 is connected to the positive (+) and neutral (N) of the first DC link stage 31 and is charged together when the first DC link stage 31 is charged, The voltage of the first DC link stage 31 can be adjusted in response to the operation of the switch 41T. The second voltage control stage 42 is connected to the neutral point N and the negative terminal (-) of the second DC link stage 32 and is charged together when the second DC link stage 32 is charged. The voltage of the second DC link stage 32 can be adjusted corresponding to the operation of the second DC link terminal 42T.

The first charge storage section 41C of the first voltage control stage 41 and the second charge storage section 42 of the second voltage control stage 42 are connected to the first DC link stage 31 and the second The DC link stage 32 may be formed of a capacitor having the same electrical characteristics or an energy storage system (ESS) having the same storage capacity.

 The first voltage control stage 41 and the second voltage control stage 42 are connected to each other when the first DC link stage 31 and the second DC link stage 32 are charged to more than the set voltage, So that the voltages of the first DC link stage 31 and the second DC link stage 32 are in an equilibrium state. Therefore, the inverter section 50 can smoothly synthesize the alternating current.

The inverter unit 50 has a structure in which a plurality of leg portions 51, 52 and 53 connected in parallel in parallel to a plurality of semiconductor switches T I1 to T I12 are connected in parallel, . Each of the leg portions 51, 52, and 53 includes first switches T I1 , T I5 , and T I9 , (T I2 , T I6 , T I10 ), a third switch (T I3 , T I7 , T I11 ) and a fourth switch (T I4 , T I8 , T I12 ) are connected in series. The inverter unit 50 further includes a first diode D1 connected to the connection point between the first switches T I1 , T I5 and T I9 and the second switches T I2 , T I6 and T I10 and the neutral point N, as connected in anti-parallel and, a first diode (D1) connected in series, the connection point and a neutral point of the third switch (T I3, T I7, T I11) and the fourth switch (T I4, T I8, T I12) (N And the second diodes D2 are connected in antiparallel with each other.

The inverter unit 50 is connected in parallel to the DC link unit 30 so that the DC output from the DC link unit 30 can be changed to an alternating current and supplied to the lower stage 70, Can be rectified to a direct current and supplied to the DC link unit 30.

The inverter unit 50 can output a three-phase power source having a phase difference of 120 degrees from the DC link unit 30 through the operation of the leg portions 51, 52 and 53 and supply the three-phase power source to the loading stage 70. Furthermore, the inverter unit 50 can apply a smooth sinusoidal wave to the lower stage 70, including the filter unit 60 composed of a resistor and an inductor that can remove the noise of the outputted sinusoidal wave.

Hereinafter, with reference to FIG. 2 to FIG. 7, a description will be given of a state where the first DC link stage and the second DC link stage are changed from the voltage unbalanced state to the voltage unbalanced state.

The transformer 11 transforms the three-phase voltage applied from the high-voltage voltage source 10 in accordance with the connection and applies it to the converter section 22. [

Converter section 22 may all be formed of a semiconductor switch (T c1 to c12 T) element. However, the semiconductor switches T c1 to T c12 may be subject to errors due to a slight error generated during the manufacturing process or an error generated from the operating environment. Such a switching error may cause a power loss so that the magnitudes of the charged voltage of the first DC link stage 31 and the second DC link stage 32 connected to the respective converter sections 21 and 22 become unbalanced . For example, assuming that the set voltage is 2650 Vdc, the switching of the semiconductor switches T C1 to T C6 of the converter section 22 causes an error in the switching of the semiconductor switches T C7 to T C12 of the converter section 22 3 (a), the first DC link stage 31 may be charged with an overvoltage of 2782.5 Vdc, which is 5% higher than the set voltage. As shown in FIG. 3 (b), the second DC link stage 32 may be charged with a voltage that is 5% less than the set voltage, that is, 2517.5 Vdc.

4, when the second DC link stage 32 is overcharged than the first DC link stage 31 and is in a voltage unbalanced state, the semiconductor switches T C7 to T C12 of the converter section 22 are turned on, switching the semiconductor switch 5% below the voltage that is, 2517.5Vdc is charged above the set voltage to a first DC link terminal 31 as shown in Figure 5 (a) because of the switching error of the (T T C7 to C12) of . As shown in Fig. 5 (b), the second DC link stage 32 can be charged with a voltage which is 5% higher than the set voltage, that is, 2782.5 Vdc.

6, when the voltage charged in the first DC link stage 31 and the second DC link stage 32 is out of the set voltage, the first voltage controller 41 controls the semiconductor switch Transfer of the charge overcharge than the set voltage of the first DC link stage 31 by the operation of the T CI1) to the first charge storage section (41C), the first DC link stage (31) controlled so that the charging set voltage . The second voltage control unit 42 replenishes the second charge storage unit 42C by an amount of electric charge that is lower than the set voltage of the second DC link stage 32 by the operation of the semiconductor switch T CI2 , So that the DC link end 32 is charged to the set voltage.

7, the voltage charged in the first DC link stage 31 and the second DC link stage 32 is set by the first voltage controller 41 and the second voltage controller 42, That is, it is adjusted to be balanced to 2650 Vdc.

 While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, You can understand that you can. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

1: bidirectional power converter 10: high voltage power source
11: Transformer 21: LC filter unit
22: Converter section 30: DC link section
31: first DC link stage 32: second DC link stage
40: voltage control unit 41: first voltage control stage
42: second voltage control stage 50: inverter section
22a, 22b, 22c, 51, 52, 53:
60: filter unit 70:
N: Neutral point

Claims (5)

A transformer for receiving a voltage from a high voltage source and transforming the voltage;
A converter connected to the transformer for rectifying the alternating current into direct current or converting direct current into alternating current;
A DC link unit connected in parallel to the converter unit and including a first DC link stage storing rectified electrical energy and a second DC link stage connected in series with the first DC link stage to form a neutral point;
A voltage control unit connected in parallel to the DC link unit and controlling a voltage level of the DC link unit;
And an inverter unit connected in parallel to the DC link unit to convert the DC output from the DC link unit into AC and supply the DC output to the lower stage or to rectify the back electromotive force introduced from the lower stage to DC and supply the direct current to the DC link unit However,
Wherein the voltage control unit further includes a semiconductor switch and a charge storage unit connected in parallel to the semiconductor switch for storing the electrical energy,
Wherein the charge storage section includes a first charge storage section connected to the anode of the first DC link stage and the neutral point and a second charge storage section connected to the neutral point and the cathode of the second DC link stage, The storage unit and the second charge storage unit are elements having the same electrical characteristics as the DC link unit,
The voltage control unit charges or discharges the first charge storage unit and the second charge storage unit when the voltage charged in the first DC link stage and the second DC link stage is out of the set voltage, And adjusts the voltage of the first DC link stage and the voltage of the second DC link stage to be balanced. delete delete The bidirectional power converter of claim 1, wherein the converter unit and the inverter unit include a plurality of legs connected in series to a plurality of semiconductor switches in a diode-parallel fashion, the legs being connected in parallel with each other. 5. The semiconductor device according to claim 4, wherein the leg portion has a first switch, a second switch, a third switch, and a fourth switch connected in series, and a connection point between the first switch and the second switch, Further comprising a second diode connected in parallel and connected in series with the first diode, the second diode being connected in parallel to the connection point of the third switch and the fourth switch and the neutral point.
KR1020150151312A 2015-10-29 2015-10-29 Bidirectional converter KR101792824B1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20230076248A (en) 2021-11-24 2023-05-31 경북대학교 산학협력단 3­level Neutral Point Clamped Converter for Capacitor Ripple Reduction Using Zigzag Transformer

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102549613B1 (en) * 2021-01-28 2023-06-29 부경대학교 산학협력단 Devices and Method for Controlling the DC-link Voltage Balancing for Modular Converters
KR102554948B1 (en) 2021-06-23 2023-07-13 경북대학교 산학협력단 Bi-directional power conversion system with wide DC bus control range

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010172141A (en) * 2009-01-23 2010-08-05 Sanken Electric Co Ltd Three-phase power conversion apparatus
KR101094002B1 (en) * 2009-12-16 2011-12-15 삼성에스디아이 주식회사 Power converting device
US20120267902A1 (en) * 2009-12-24 2012-10-25 Doosan Infracore Co., Ltd. Power converting device for hybrid

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010172141A (en) * 2009-01-23 2010-08-05 Sanken Electric Co Ltd Three-phase power conversion apparatus
KR101094002B1 (en) * 2009-12-16 2011-12-15 삼성에스디아이 주식회사 Power converting device
US20120267902A1 (en) * 2009-12-24 2012-10-25 Doosan Infracore Co., Ltd. Power converting device for hybrid

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20230076248A (en) 2021-11-24 2023-05-31 경북대학교 산학협력단 3­level Neutral Point Clamped Converter for Capacitor Ripple Reduction Using Zigzag Transformer

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